Very often a true, representative sample of the fluid in a well is desired but not necessarily obtained. A current problem in secondary oil recovery, for example, is the need for a sample of the injected polymer in an injection well at the depth of the intended injection interval. After this polymer has entered the formation and backflowed thereafter, it must be sampled without having its physical properties altered as it is lifted to the surface for analyzing and testing. An additional example is the need to sample polymer which has flowed through the oil bearing formation from the injection well to the producing well. This sample must also be obtained and lifted to the surface without altering its physical properties.
Various problems arise in obtaining the sample of the well fluid. First, the injection well fluid or polymer is stagnant and so the polymer must be made to flow into the sampler. Second, and most importantly, most polymers cannot be subjected to high shear rates which occur during high flow rates. Conventional bottom hole samplers enter the well with the sample chamber at atmospheric pressure and when opened in the wellbore at the formation depth will rapidly fill exposing the sample to very high shear rates. The high shear rates particularly alter the physical properties of the polymer and accordingly produce a non-representative sample. The method and sampler disclosed herein provide a true and representative sample from the perforated interval, for example.